During normal use, contact lenses become soiled or contaminated with a wide variety of compounds that can degrade lens performance. For example, a contact lens will become soiled with biological materials such as proteins or lipids that are present in the tear fluid and which adhere to the lens surface. Also, by handling of the contact lens, sebum (skin oil) or cosmetics or other materials can soil the contact lens. These biological and external contaminants can affect visual acuity and patient comfort during use and at the end of the day. Accordingly, it is important to remove any debris from the lens surface for continued comfortable use with a lens care cleaning and disinfecting solution that contains one or more cleaning components. It can also be important that a lens care cleaning and disinfecting solution provide a contact lens consumer with some level of ocular comfort or hydration, particularly, consumers diagnosed with keratoconjunctivitis sicca, a condition often referred to as dry eye syndrome.
Dry eye is a common ophthalmological disorder affecting millions of people. A patient with dry eye may experience burning, a feeling of dryness, and persistent irritation. In severe cases, dry eye can seriously impair a person's vision. Also, as people age the lacrimal glands in the eye may produce less tears, resulting in eyes that become dry, inflamed, itchy, and gritty. More than 50% of total patients visiting ophthalmic clinics report dry eye syndromes. The elderly, particularly 70 to 80% of post-menopausal women suffer from ocular discomfort due to dry eye. Although it appears that dry eye may result from a variety of unrelated pathogenic causes, all presentations of the condition share a common feature, namely the breakdown of the precorneal tear film that results in dehydration of the exposed outer ocular surface and hence the symptoms described.
A number of approaches exist for the treatment of dry eye. One common approach has been to supplement the ocular tear film using artificial tears instilled throughout the day. Examples of the tear substitute approach include the use of buffered, isotonic saline solutions and aqueous solutions containing water-soluble polymers that render the solutions more viscous and thus less easily shed by the washing action of tear fluid. See, for example, U.S. Pat. No. 5,209,927 to Gressel et al.; U.S. Pat. No. 5,294,607 to Glonek et al.; and U.S. Pat. No. 4,409,205 to Shively.
Natural waxes are often found as trace components of triglyceride oils or can be extracted from certain botanical and animal sources. Sunflower and corn oils contain natural waxes, while jojoba, carnauba and candelillia are examples of waxes found naturally in a more pure form. Beeswax and lanolin are examples of natural waxes of insect and animal origin. These example waxes range from the liquid, unsaturated jojoba oil to the almost completely saturated sunflower wax. In order to control or modify various properties of natural oils and waxes such as water solubility, one can form alkoxylated derivatives. For example, by controlling the number of ethylene oxide (ETO) and/or propylene oxide (PO) units that one can attach to the hydroxyl function of the natural waxes various properties such as solubility and melting point can be modified. Generally, it has been found that the natural oils and waxes become more water soluble as the level of alkoxylation increases. Compounds that are ethoxylated, as well as propoxylated, become more water and alcohol soluble.
Lanolin also called Adeps Lanae, wool wax or wool grease, is a yellow waxy substance secreted by the sebaceous glands of sheep. Lanolin is also frequently, but incorrectly, referred to as wool wat even though it well known that lanolin is essentially devoid of glycerides and is in fact a wax, not a fat. Like many natural products, lanolin has a complex and variable composition. For example, a typical high purity grade of lanolin is composed predominantly of long chain waxy esters (ca. 97% by weight) the remainder being lanolin alcohols, lanolin acids and lanolin hydrocarbons. Lanolin's role in nature is to protect wool and skin against the ravages of climate and the environment—it also seems to play a role in integument hygiene. It is therefore not surprising that lanolin and its many derivatives are used extensively in products designed for the protection, treatment and beautification of human skin.
Poly(ethoxylate) lanolin or PEG lanolin is a commercially available. PEG lanolin is derived from lanolin by a chemical process that adds ethoxylate linkages to the hydroxyl functionality of lanolin. PEG lanolin is a flaky wax at room temperature with a slight yellow to amber color. PEG75 lanolin has polymer chains with a mean length of 75 ethylene oxide units, and the resulting compound has a weight average molecular weight (MW) of about 3500 dalton with a lanolin ester core and a polyethylene oxide chain. PEG75 lanolin is a water-soluble derivative of lanolin as a result of ethoxylation. The surrounding polyether chain allows water molecules to assemble around the non-polar and otherwise virtually water insoluble lanolin ester core. The resulting aqueous solutions are clear with a feint yellow color that increases with concentration, non-ionic and compatible with most physiological electrolytes, e.g. sodium chloride.
Jojoba is a shrub native to the Sonoran and Mojave deserts of Arizona, California, and Mexico. Jojoba is grown commercially for its oil, a liquid wax ester, expressed from the seed. The oil is rare in that it is an extremely long (C36-C46) straight-chain wax ester and not a triglyceride, making jojoba and its derivative jojoba esters more similar to human sebum and whale oil than to traditional vegetable oils. Jojoba oil is easily refined to be odorless, colorless and oxidatively stable, and is often used in cosmetics as a moisturizer and as a carrier oil for specialty fragrances. U.S. Patent Pub. No. 20050202097 describes a formulation for treatment of the symptoms of dry eye that includes natural jojoba wax, or components thereof, and is said to relieve ocular irritation and discomfort associated with dry eye.
Poly(ethoxylate) jojoba or PEG jojoba is available as a commercial source of an alkoxylated jojoba. Like PEG lanolin, PEG jojoba is derived from jojoba oil by a chemical process that adds ethoxylate linkages to the hydroxyl functionality of the oil. PEG jojoba is a flaky, off-white wax at room temperature. PEG150 jojoba has polymer chains with a mean length of 150 ethylene oxide units. PEG jojoba is a completely water-soluble derivative of jojoba oil as a result of ethoxylation.
U.S. patent application Ser. No. 12/571,465 filed Oct. 1, 2009 relates to contact lens care solutions with a cationic antimicrobial component, and a low molecular weight cationic or nitrogen/amine-based oligomer. The number average molecular weight of the cationic or nitrogen/amine-based oligomer is in the range of 500 daltons to 15,000 daltons, and is believed to compete with the cationic antimicrobial component for the pores or surface sites of contact lens materials. The result is a contact lens care solution with improved biocidal efficacy over time and improved comfort to the patient.